FRONT-END CIRCUIT FOR AN ULTRASOUND TRANSDUCER PROBE
The present invention relates to an ultrasound transducer probe 100 having an array of transducer elements 110 for transmitting ultrasound transmit pulses and receiving echo signals in response to these transmit pulses. More precisely, the invention refers to a front-end circuit 300, 300′ or 300″ preconnected to such an ultrasound transducer probe, wherein said front-end circuit, which may e.g. be realized as an application-specific integrated circuit (ASIC) with given input voltage constraints prescribing a limited supply voltagein1, comprises a transmission stage 301 which includes a branched voltage control line 302 or lines with two transmit branches 302a and 302b being respectively connected to a different terminal of each transducer element 110 for providing each of these transducer elements with a differential excitation or pulse voltageop whose amplitude level is up to twice the voltage levelin1 of the single-ended front-end circuit 300, 300′ or 300″ which is supplied by voltage control line 302.
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The present invention relates to an ultrasound transducer probe (scanhead) having an array of transducer elements for transmitting ultrasound transmit pulses and receiving echo signals in response to these transmit pulses. More precisely, the invention refers to a front-end circuit preconnected to such an ultrasound transducer probe, wherein said front-end circuit, which may e.g. be realized as an application-specific integrated circuit (ASIC) with given input voltage constraints prescribing a limited supply voltage, comprises a transmission stage, said transmission stage comprising a branched voltage control line or lines with two transmit branches being respectively connected to a different terminal of each transducer element for providing each of these transducer elements with a differential excitation or pulse voltage whose amplitude level is up to twice the voltage level of the single-ended front-end circuit which is supplied by said voltage control line. In this context, a bridged amplifier topology is proposed which comprises at least one transmit amplifier or pulser integrated in each one of the two transmit branches, wherein the transmit amplifier in a first one of these transmit branches provides an output signal corresponding to the non-inverted input signal and the transmit amplifier in a second one of said transmit branches provides an output signal corresponding to an inverted form of said input signal such that up to twice the voltage amplitude of the ultrasound transducer's front-end supply voltage is lying across each transducer element without needing to provide this doubled voltage level at the voltage supply inputs of the application-specific integrated circuit, thus being able to use the same IC fabrication process to get twice the voltage swing over the transducer elements.
BACKGROUND OF THE INVENTIONUltrasound medical diagnostic systems are used to generate sonography images of anatomical structures within a patient's body by scanning a target area with ultrasound signals. Typically, ultrasound signals in the order between 2.0 MHz and 10 MHz are transmitted into a patient via an ultrasound transducer probe. The transmitted ultrasound energy is in part absorbed, dispersed, refracted, and reflected by the patient's body, and the reflected ultrasound energy is received at the transducer probe where it is converted into electronic echo signals which can be evaluated and further processed. In many conventional ultrasound systems, it may e.g. be provided that received echo signals undergo a beamforming. Subsequently, the beamformed signals may be processed to analyze echo, Doppler, and flow information and to obtain a sonography image of a targeted anatomy structure or tissue region of interest in the interior of the patient's body.
SUMMARY OF THE INVENTIONIn conventional designs of compact portable ultrasound machines which are available on the market today, the front-end circuit may be equipped with a transmitter unit implemented by an integrated circuit with given input voltage constraints prescribing a limited supply voltage, and it may be that the process used to fabricate this integrated circuit is not able to handle those high voltage levels which are usually required and desired for traditional ultrasound probes to get sufficient acoustic transmit power. For other applications, e.g. catheters and internal probes, such as e.g. endoscopic ultrasound probes for use in transesophageal echocardiography (TEE), it might be necessary to use probes with lower voltages in order to reduce any potential risks to the patient and to minimize the probe's size by providing thinner insulation layers.
An object of the present invention is thus to find a way to integrate the transmitting part (and also the receiving part) of a front-end circuit into an ultrasound machine while considering the above-mentioned constraints concerning the front end circuit's output power and the integrated circuit's input voltage. In this context, the present invention particularly aims at solving the problem of obtaining a higher transmit voltage without needing to change the process used to fabricate the front-end's integrated circuits.
In view of this object, a first exemplary embodiment of the present application refers to a front-end circuit of an ultrasound transducer probe having an array of differentially connected transducer elements for transmitting ultrasound transmit pulses and receiving echo signals in response to these transmit pulses, wherein said front-end circuit comprises a transmission stage with two separate transmit branches being respectively connected to a different terminal of each transducer element for providing each of these transducer elements with a differential excitation or pulse voltage whose amplitude level is given by the difference of the front-end circuit's input control signals which are fed via the two transmit branches to the respective transducer element.
According to a first aspect of this embodiment, the proposed front-end circuit may further comprise a bridged amplifier topology having at least one transmit amplifier integrated in each one of the two transmit branches which are used for providing each transducer element with the differential excitation or pulse voltage, wherein the transmit amplifier in a first one of these transmit branches provides a first output signal which is given by one of the front-end circuit's input control signals in a non-inverted form after being amplified by a gain factor and wherein the transmit amplifier in a second one of these transmit branches provides a second output signal which is given by the same input control signal in an inverted form after being amplified by the same gain factor. For example, if said input control signal is given by an input voltage, it can thus be provided that the amplitude level of the differential excitation or pulse voltage is up to twice the voltage level of this input voltage.
The transmit amplifiers may thereby be implemented as two linear amplifiers that are controlled by a linear input control signal. In this case (which represent one preferred embodiment of the present invention), the non-inverted input control signal is supplied to one amplifier and the inverted input control signal is fed to the other amplifier. The same effect could be achieved by having one of the two amplifiers be an inverting amplifier, in which case both amplifiers could be supplied with the same input control signal.
Alternatively, according to a second aspect of this embodiment, the proposed front-end circuit may comprise a bridged amplifier topology having at least one transmit pulser integrated in each one of the two transmit branches which are used for providing each transducer element with the differential excitation or pulse voltage, wherein the transmit pulser in a first one of these transmit branches provides a first output signal whose amplitude level is set by a first set of digital control signals fed to an input terminal of the transmit pulser in this first transmit branch and wherein the transmit pulser in a second one of these transmit branches provides a second output signal whose amplitude level is set by a second set of digital control signals fed to an input terminal of the transmit pulser in this second transmit branch.
The particular amplifiers (or pulsers) are thereby operated in a bridged mode. Each transducer element is thus connected across the output ports of two associated amplifiers and is supplied with up to twice the voltage level of the input voltage fed to said amplifiers' voltage supply terminals. Using such a circuit topology means in effect to double the number of used amplifiers. The proposed circuit makes it possible to double the amplitude level of the single-ended supply voltage at the supply port of the front-end circuit with the same IC process and further implies the advantage of obtaining a higher transmit power and therefore increased penetration or signal-to-noise ratio without needing to change the existing scanhead acoustic design and without needing to increase the amplitude level of the front-end circuit's supply voltage relative to a ground potential. Furthermore, the proposed front-end circuit allows the use of a less expensive scanhead design in case it is intended to maintain transmit power instead of increasing it or to do trade-offs between transmit power, penetration, signal-to-noise ratio and acoustic stack design and cost.
According to a specific aspect of the present invention, it may further be provided that the output ports of the transmit amplifiers or transmit pulsers are connected by a flip chip, flex circuit or other type of interconnect to an associated transducer element of the transducer array. That is, the front-end amplifiers are in the same package as the transducer elements in the scanhead, thus making a long cable connection between the amplifiers and the scanhead unnecessary.
Preferably, according to a specific aspect of the present invention, it may be foreseen that the transmit amplifiers or transmit pulsers are integrated in the ultrasound transducer probe and that the proposed front-end circuit is implemented as an application-specific integrated circuit of the ultrasound transducer probe.
According to the present invention, the proposed front-end circuit may further comprise a differential reception stage which provides an output signal representing said echo signals. The reception stage may thereby connect each terminal of the at least one transducer element to an associated low-noise amplifier.
Aside therefrom, the present invention also refers to a new type of ultrasound transducer probes. Whereas conventional scanheads are equipped with single-ended transducer elements having a common ground potential, said transducer elements being supplied with two wires for ground and signal, it may be provided that the proposed ultrasound transducer probe is equipped with differentially connected transducer elements, i.e. with transducer elements which do not have any ground electrode.
Therefore, a second exemplary embodiment of the present application relates to an ultrasound diagnostic imaging system which comprises an ultrasound transducer probe having an array of differentially connected transducer elements for transmitting ultrasound transmit pulses and receiving echo signals in response to these transmit pulses. According to the present invention, it may thereby be provided that said system is equipped with an integrated front-end circuit as described above with reference to said first exemplary embodiment.
According to a preferred aspect of this second exemplary embodiment, the claimed ultrasound diagnostic imaging system may advantageously be equipped with an integrated microbeamformer system.
These and other advantageous features and aspects of the invention will be elucidated by way of example with respect to the embodiments described hereinafter and with respect to the accompanying drawings. Therein,
In the following, different embodiments of the present invention will be explained in detail with respect to special refinements and referring to the accompanying drawings.
Conventionally, ultrasonic transducers assemblies such as transducer probe 100 are connected to the base ultrasound system 130 by a cable 120. The base ultrasound system 130 comprises processing and control equipment 132, as well as the display 133. Those skilled in the art will note that the transducer probe could be readily constructed to include a wireless connection to the base ultrasound system in lieu of cable 120, and the software which drives the beamformer easily modified to receive and process the wireless signals from the transducer probe (e.g., radio transmission; see U.S. Pat. No. 6,142,946).
System components that transmit and receive the ultrasonic waves in the transducer probe may be implemented differently in various ultrasonic systems. In the ultrasound system of
One particular known beamforming practice is referred to as multi-line beamforming. In a “multiline beamforming”, the transducer array 110 transmits a single ultrasonic beam, but the receive beamformer electronics synthesize several receive ultrasonic beams with different orientations. The oldest and most basic approach to multiline beamforming is to use multiple single line beamformers that are operated in parallel, such as described in U.S. Pat. No. 4,644,795 to Augustine, which is incorporated by reference. In such an arrangement, each element in the transducer array is connected to a channel of the beamformer. Each of these channels applies delays to the signals from its corresponding element, which delays are appropriate to steer and focus the beam being formed by the beamformer. The signals delayed by each channel of the beamformer are combined to form a uniquely steered and focused beam, and the multiple beams which are produced simultaneously by parallel operated beamformers are used to form multiple lines of an ultrasound image.
An example of an ultrasound imaging system with a conventional multiple signal line beamforming architecture as known from WO 2006/035384 A1 is shown in
This approach is sufficient if the number of elements 211 being sampled in the transducer array 210 remains fairly low, i.e., under 200 or so elements (traditional beamformers have 128 channels). If the transducer array 210 has thousands of acoustic elements 211, the particular processing scheme requires that the use of samples from each of those elements, cable 220 would have to carry thousands of channels. Such a scheme would require a prohibitively large cable and more power than is available from a standard electric outlet (the typical power source for most ultrasound systems). For these and other reasons (including the excessive cost of such a cable and the associated electronics), the approach shown in
A known solution to this problem of complexity is referred to as “sub-array beamforming” or “micro-beamforming”. An example of an ultrasound imaging system with a microbeamforming architecture as known from WO 2006/035384 A1, which is capable of implementing a microbeamforming process, is sketched in
As shown in
When performing microbeamforming, different bulk delays may be applied to each sub-array signal, where each bulk delay imposes the appropriate delay on each sub-array relative to the other sub-arrays. The partially beamformed analog signals from sub-arrays 240-1 to 240-n are transmitted on channels 222-1 to 222-n over cable 220 to processing means 232 in the base ultrasound system 130. The sub-array analog signals are converted to digital by A/Ds 233, appropriately delayed by digital delays 234, and then combined by final summer 235. The bulk delays discussed in the paragraph above may be implemented by digital delays 234.
Although contiguous, the transducer elements, which comprise a sub-array, may form a variety of shapes or patterns on the transducer array. For example, in a rectangularly shaped transducer array, each column of transducer elements may form a sub-array. Such constructions are described in U.S Pat. Nos. 6,102,863, 5,997,479, 6,013,032, 6,380,766 and U.S. Pat. No. 6,491,634, each of which are incorporated by reference herein. In the U.S. Pat. No. 6,102,863 patent, “elevation” beamforming (i.e., combining the signals in each column of elements) is performed in the transducer, while “azimuth” beamforming (i.e., combining the row of previously combined columns) is performed by the processing means in the ultrasound system.
In
An analog implementation 300′ of the ultrasound transducer probe's front-end circuit 300 as depicted in
The proposed circuit thereby comprises a differential connection between a single analog line 302 (or multiple digital control lines) at the voltage supply inputs of the front-end circuit 300′ and an associated transducer element 110 (which may e.g. be given by a piezoelectric element 305) in the scanhead 100. Due to the differential circuit design, the proposed front-end circuit has no common ground potential. A front-end circuit according to the present invention may either be implemented using conventional transmit amplifiers 304a and 304b, in which a differential cable 307 is required between the front-end circuit 300′ and the particular transducer elements 110 of the transducer array in the scanhead 100. On the other hand, coaxial cables are traditionally used, which are not differential. Therefore, some other type of cables is needed, such as e.g. twisted-pair cables.
Another preferred implementation would be to implement bridged transmit amplifiers 304a and 304b in the scanhead 100. In this case, said amplifiers may be connected to the transducer elements 110 via integrated flex circuits. In this case, it would be easy to design flex circuits that directly connect to the transducer elements 110.
As illustrated in
It should be noted that
For ultrasound transducer probes where the front-end circuit is connected directly to the input ports of the transducer elements 110, a suitable acoustic design may be provided that makes it possible not to have a common ground.
A digital implementation 300″ of the ultrasound transducer probe's front-end circuit 300 as depicted in
Using a front-end circuit as described above for operating a medical probe, such as e.g. an ultrasound transducer probe (scanhead), effectively doubles the amplitude level of the front-end circuit's supply voltage and therefore quadruples the front-end circuit's achievable output power.
The invention can advantageously be applied in the field of compact ultrasound machines and other applications which require the use of a front-end integrated circuit that is fabricated using a relatively low voltage fabrication process or to reduce an ultrasound transducer probe's operating voltage for size, cost or safety reasons. The invention's main application is for low-cost, compact ultrasound machines where scanheads with an integrated beamforming functionality are used. For these applications, the present invention provides a means to use a relatively inexpensive acoustic design and serves for supplying a significantly higher excitation or pulse voltage given the voltage constraints of a given IC fabrication process.
While the present invention has been illustrated and described in detail in the drawings and in the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive, which means that the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. Furthermore, any reference signs contained in the claims should not be construed as limiting the scope of the invention.
LIST OF REFERENCE SIGNS
- 100 Ultrasonic transducer assembly (also referred to as “ultrasound transducer”, “ultrasound transducer probe” or “scanhead”)
- 101 Face of ultrasound transducer probe 100
- 110 Array of piezoelectric elements (also referred to as “transducer elements”), which both transmit and receive ultrasonic waves
- 120 Single-ended cable
- 130 Base ultrasound system
- 132 Processing and control equipment
- 133 Display
- 200 Ultrasound transducer probe
- 210 Transducer array (comprising ultrasound transducer probe 200)
- 211 Transducer elements of transducer array 210
- 220 Single-ended cable
- 221-1 First transmit channel
- 221-n n-th transmit channel
- 222a Multiplexer
- 222b Demultiplexer
- 232 Processing means
- 233 Analog-to-digital (A/D) converters
- 234 Digital delays
- 235 Summer
- 240-1 First sub-array of transducer array 210
- 240-n n-th sub-array of transducer array 210
- 241 Pre-amplifier
- 242 Low-power analog delay
- 300 Front-end circuit (simplified embodiment)
- 300′ Front-end circuit (analog implementation, more detailed embodiment)
- 300″ Front-end circuit (digital implementation, more detailed embodiment)
- 301 Transmission stage, configured as a bridged or differential amplifier
- 302 Input voltage feeding line of front-end circuit 300′
- 302a First transmit branch of front-end circuit 300, 300′ or 300″, used for supplying a first input voltage or voltage control signal Uin1 or a first set of digital control signals S1
- 302b Second transmit branch of front-end circuit 300, 300′ or 300″, used for supplying a second input voltage or voltage control signal Uin2 (wherein Uin2 may be given by Uin1 in an inverted form as supplied by inverter 303) or a second set of digital control signals S2
- 303 Inverter or digital control circuit, integrated in second transmit branch 302b
- 304a High-voltage transmit amplifier stage, integrated in the first transmit branch 302a of the analog front-end circuit 300′
- 304a′ Transmit pulser stage, integrated in the first transmit branch 302a of the digital front-end circuit 300″
- 304b High-voltage transmit amplifier stage, integrated in the second transmit branch 302b of the analog front-end circuit 300′
- 304b′ Transmit pulser stage, integrated in the second transmit branch 302b of the digital front-end circuit 300″
- 305 Transducer element (e.g. a piezoelectric elements made of lead zirconate titanate or other material), belonging to an array of transducer elements which are integrated in scanhead 100
- 306 Differential reception stage
- 307 Differential cable, flex circuit or other electrical interconnect between differential amplifier stages 304a/b and transducer element 305
- k Gain of amplifiers 304a and 304b
- S1 First set of digital control signals, fed to high-voltage transmit amplifier stage 304a
- S2 Second set of digital control signals, fed to high-voltage transmit amplifier stage 304b
- t Continuous time variable
- Uin1 Analog input voltage or voltage control signal of front-end circuit 300 or 300′
- Uin2 Further analog input voltage or voltage control signal of front-end circuit 300 or 300′
- ±UHV Positive and negative supply voltage potential of high-voltage transmit amplifier stages 304a and 304b
- Uop Excitation or pulse voltage of transducer element 305
- Uop1 Output signal of high-voltage transmit amplifier stage 304a
- Uop1,max Maximum level of output signal Uop1
- Uop2 Output signal of high-voltage transmit amplifier stage 304b
- Uop2,min Minimum level of output signal Uop2
- Uout Output signal of receive amplifier 306 at the output port of front-end circuit 300, 300′ or 300″ (can either be single-ended or differential)
Claims
1. An ultrasound transducer probe (100) comprising,
- an array of differentially connected transducer elements (110) for transmitting ultrasound transmit pulses and receiving echo signals in response to these transmit pulses,
- a front-end circuit (300, 300′ or 300″) comprising a transmission stage (301) with two separate transmit branches (302a, 302b) being respectively connected to a different terminal of each transducer element (110) for providing each of these transducer elements (110) with a differential excitation or pulse voltage (Uop) whose amplitude level is given by the difference (Uop1-Uop2) with Uop1 and Uop2 being given by the front-end circuit's input control signals (Uin1, Uin2) which are fed via the two transmit branches (302a, 302b) to the respective transducer element (110).
2. An ultrasound transducer probe according to claim 1, comprising a bridged amplifier topology having at least one transmit amplifier (304a, 304b) integrated in each one of the two transmit branches (302a, 302b) which are used for providing each transducer element (110) with the differential excitation or pulse voltage (Uop), wherein the transmit amplifier (304a) in a first one (302a) of these transmit branches provides a first output signal (Uop1) which is given by one of the front-end circuit's input control signals in a non-inverted form (+k·Uin1) after being amplified by a gain factor (k) and wherein the transmit amplifier (304b) in a second one (302b) of these transmit branches provides a second output signal (Uop2) which is given by the same input control signal in an inverted form (−k·Uin1) after being amplified by the same gain factor (k).
3. An ultrasound transducer probe according to claim 1, comprising a bridged amplifier topology having at least one transmit pulser (304a′, 304b′) integrated in each one of the two transmit branches (302a, 302b) which are used for providing each transducer element (110) with the differential excitation or pulse voltage (Uop), wherein the transmit pulser (304a′) in a first one (302a) of these transmit branches provides a first output signal (Uop1) whose amplitude level is set by a first set of digital control signals (S1) fed to an input terminal of the transmit pulser (304a′) in this first transmit branch (302a) and wherein the transmit pulser (304b′) in a second one (302b) of these transmit branches provides a second output signal (Uop2) whose amplitude level is set by a second set of digital control signals (S2) fed to an input terminal of the transmit pulser (304b′) in this second transmit branch (302b).
4. An ultrasound transducer probe according to claim 2, wherein the output ports of the transmit amplifiers (304a, 304b) or transmit pulsers (304a′, 304b′) are connected by a flip chip, flex circuit or other type of interconnect to an associated transducer element (110) of said array.
5. An ultrasound transducer probe according to claim 4, wherein the transmit amplifiers (304a, 304b) or transmit pulsers (304a′, 304b′) are integrated in the ultrasound transducer probe (100).
6. An ultrasound transducer probe according to claim 5, implemented as an application-specific integrated circuit of the ultrasound transducer probe (100).
7. An ultrasound transducer probe according to claim 6, comprising a differential reception stage (306) which provides an output signal (Uout) representing said echo signals.
8. An ultrasound transducer probe according to claim 7, wherein said reception stage connects each terminal of the at least one transducer element (110) to an associated low-noise amplifier.
9. An ultrasound transducer probe according to claim 8, wherein each transducer element (110) is realized as a piezoelectric element (305).
10. An ultrasound diagnostic imaging system, said system comprising an ultrasound transducer probe (100) as defined in claim 1.
11. An ultrasound diagnostic imaging system according to claim 10, equipped with an integrated microbeamformer system.
Type: Application
Filed: Dec 1, 2009
Publication Date: Sep 29, 2011
Applicant: KONINKLIJKE PHILIPS ELECTRONICS N.V. (EINDHOVEN)
Inventors: Lars Jonas Olsson (Woodinville, WA), Andrew Robinson (Bellevue, WA), Richard Betts (Seattle, WA)
Application Number: 13/132,636
International Classification: A61B 8/14 (20060101);